本論文研究主題主要是利用摻雜偶氮苯環旋性物質Ql-3c-S於膽固醇液晶中的光致同分異構化反應，藉由擾動液晶分子排列來調控膽固醇液晶planar結構之螺距，進而改變入射光之反射頻譜。由於光致同分異構化為可逆反應，所以本實驗將利用兩道不同波長的光讓偶氮苯環旋性物質在trans-isomer和cis-isomer兩種結構中互相轉換，利用此可逆反應製造出可光控濾波器。
　　在光濾波器設計方面，本論文將分為兩大部分，第一部分主要是結合兩片可光控膽固醇液晶樣品於反射式的實驗架構下，入射光經由第一片樣品會反射和膽固醇液晶相同旋性之圓偏振，其反射之頻寬再經由第二片樣品選擇性反射，製造出可調中心波長及頻寬之光控濾波器，其中心波長可調範圍從510 nm – 627.89 nm，最窄頻寬為13.31 nm。
　　第二部分則是結合高分子膽固醇液晶薄膜與可光控膽固醇液晶，將其作為單一樣品，兩者在相同旋性膽固醇結構下，製做可光控帶拒濾波器；而結合相反旋性的膽固醇液晶結構，可提高光控帶通濾波器之反射效率，且反射效率可調範圍從41 % – 83 %。

關鍵詞：膽固醇液晶，偶氮苯環旋性物質，濾波器。

This thesis studies the photo-isomerization effect in cholesteric liquid crystals (CLCs) doped with an azobenzene-chiral (azo-chiral) dopant, Ql-3c-S. The photo-isomerization effect induces the change of pitch in the CLC planar structure, and the reflection spectrum of a white light being incident onto it. Since the photo-isomerization is reversible, it allows us to switch azo-chiral dopant molecule between trans- and cis- isomer using two pump beams with different wavelengths. In view of this, we can take advantage of it to fabricate photo-tunable optical filter .
　　In the present design of the photo-tunable optical filter, the studies are divided into two parts. The first part demonstrates the photo-tunable filter using two photo-tunable CLC cells configured in a reflection mode. The incident light is firstly reflected by the first sample with the same circular polarization of CLC. The reflection band from the first sample is selective reflected by the other one. The photo-tunable reflection wavelength and band of the fabricated sample composed of two CLC doped with azo-chiral are demonstrated. The central wavelength can be switching from 510 nm to 627.89 nm with the narrowest bandwidth of being 13.31 nm.
　　The second experiment investigates the filter composed cholesteric liquid crystal polymer (CLCP) and photo-tunable CLC. Combining CLCP with photo-tunable of the same chirality, we demonstrate that the formed sample is able to be used as a photo-tunable band-stop filter. Moreover, combined CLCP with photo-tunable of opposite chirality, the formed sample is demonstrated to function as a photo-tunable band-pass filter with high reflection, its reflectivity can be control from 41% to 83 %.

Keywords: cholesteric liquid crystals, azo-chiral, optical filter.

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